Atlas of Anatomy

25 Knee & Leg

Tibia & Fibula

images The tibia and fibula articulate at two joints, allowing limited motion (rotation). The crural interosseous membrane is a sheet of tough connective tissue that serves as an origin for several muscles in the leg. It also acts with the tibiofibular syndesmosis to stabilize the ankle joint.

Fig. 25.1   Tibia and fibula
Right leg.

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Fibular fracture

When diagnosing a fibular fracture, it is important to determine whether the syndesmosis (see p. 380) is disrupted. Fibular fractures may occur distal to, level with, or proximal to the syndesmosis; the latter two frequently involve tearing of the syndesmosis.

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In this fracture, located proximal to the syndesmosis, the syndesmosis is torn, as indicated by the widened medial joint space of the upper ankle joint (see p. 405).

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Knee Joint: Overview

images In the knee joint, the femur articulates with the tibia and patella. Both joints are contained within a common capsule and have communicating articular cavities. Note: The fibula is not included in the knee joint (contrast to the humerus in the elbow; see p. 282). Instead, it forms a separate rigid articulation with the tibia.

Fig. 25.2   Right knee joint

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Fig. 25.3   Knee joint: Radiographs

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Fig. 25.4   Patella

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Knee Joint: Capsule, Ligaments & Bursae

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Fig. 25.5   Ligaments of the knee joint
Anterior view of right knee.

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Fig. 25.6   Capsule, ligaments, and periarticular bursae
Posterior view of right knee. The joint cavity communicates with periarticular bursae at the subpopliteal recess, semimembranosus bursa, and medial subtendinous bursa of the gastrocnemius.

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Gastrocnemio-semimembranosus bursa (Baker's cyst)

Painful swelling behind the knee may be caused by a cystic outpouching of the joint capsule (synovial popliteal cyst). This frequently results from a rise in intra-articular pressure (e.g., in rheumatoid arthritis).

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Knee Joint: Ligaments & Menisci

Fig. 25.7   Collateral and patellar ligaments of the knee joint
Right knee joint. Each knee joint has medial and lateral collateral ligaments. The medial collateral ligament is attached to both the capsule and the medial meniscus, whereas the lateral collateral ligament has no direct contact with either the capsule or the lateral meniscus. Both collateral ligaments are taut when the knee is in extension and stabilize the joint in the coronal plane.

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Fig. 25.8   Menisci in the knee joint
Right tibial plateau, proximal view.

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Injury of the menisci

The less mobile medial meniscus is more susceptible to injury than the lateral meniscus. Trauma generally results from sudden extension or rotation of the flexed knee while the leg is fixed.

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Fig. 25.9   Movements of the menisci
Right knee joint.

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Cruciate Ligaments

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Fig. 25.10   Cruciate and collateral ligaments
Right knee joint. The cruciate ligaments keep the articular surfaces of the femur and tibia in contact, while stabilizing the knee joint primarily in the sagittal plane. Portions of the cruciate ligaments are taut in every joint position.

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Fig. 25.11   Right knee joint in flexion
Anterior view with joint capsule and patella removed.

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Rupture of cruciate ligaments

Cruciate ligament rupture destabilizes the knee joint, allowing the tibia to move forward (anterior "drawer sign") or backward (posterior "drawer sign") relative to the femur. Anterior cruciate ligament ruptures are approximately 10 times more common than posterior ligament ruptures. The most common mechanism of injury is an internal rotation trauma with the leg fixed. A lateral blow to the fully extended knee with the foot planted tends to cause concomitant rupture of the anterior cruciate and medial collateral ligaments, as well as tearing of the attached medial meniscus.

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Fig. 25.12   Cruciate and collateral ligaments in flexion and extension
Right knee, anterior view. Taut ligament fibers in red.

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Knee Joint Cavity

Fig. 25.13   Joint cavity
Right knee, lateral view. The joint cavity was demonstrated by injecting liquid plastic into the knee joint and later removing the capsule.

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Fig. 25.14   Opened joint capsule
Right knee, anterior view with patella reflected downward.

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Fig. 25.15   Attachments of the joint capsule
Right knee joint, anterior view.

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Fig. 25.16   Suprapatellar pouch during flexion
Right knee joint, medial view.

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Fig. 25.17   Right knee joint: Midsagittal section

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Fig. 25.18   MRI of knee joint
Sagittal T2-weighted MRI.

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Muscles of the Leg: Anterior & Lateral Views

Fig. 25.19   Muscles of the leg: Anterior view
Right leg. Muscle origins (O) shown in red, insertions (I) in blue.

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Fig. 25.20   Muscles of the leg: Lateral view
Right leg.

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Muscles of the Leg: Posterior View

Fig. 25.21   Muscles of the leg: Posterior view
Right leg. Muscle origins (O) shown in red, insertions (I) in blue.

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Muscle Facts (I)

images The muscles of the lower leg control the flexion/extension and supination/pronation of the foot as well as provide support for the knee, thigh, hip, and gluteal muscles.

Fig. 25.22   Lateral compartment
Right leg and foot.

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Fig. 25.23   Anterior compartment
Right leg, anterior view.

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IP = interphalangeal; MTP = metatarsophalangeal.

Muscle Facts (II)

images The muscles of the posterior compartment are divided into two groups: the superficial and deep flexors. These groups are separated by the transverse intermuscular septum.

Fig. 25.24   Superficial flexors
Right leg, posterior view.

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Fig. 25.25   Deep flexors
Right leg with foot in plantar flexion, posterior view.

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